Log Levels Guide

Standard Log Levels

Logly provides 8 standard log levels with specific priorities:

Usage

#![allow(unused)]
fn main() {
use logly::prelude::*;

let logger = Logger::new();

logger.trace("Detailed trace information".to_string())?;
logger.debug("Debug information".to_string())?;
logger.info("Application started".to_string())?;
logger.success("Operation completed successfully!".to_string())?;
logger.warning("Warning message".to_string())?;
logger.error("Error occurred".to_string())?;
logger.fail("Operation failed".to_string())?;
logger.critical("Critical system error!".to_string())?;
}

Level Filtering

Set minimum log level to filter messages:

#![allow(unused)]
fn main() {
let mut config = LoggerConfig::default();
config.level = Level::Warning;  // Only WARNING and above
logger.configure(config);

logger.debug("Not shown".to_string())?;
logger.warning("Shown".to_string())?;
logger.error("Shown".to_string())?;
}

Custom Log Levels

Add your own log levels with custom priorities and colors:

#![allow(unused)]
fn main() {
// Add custom level between WARNING (30) and ERROR (40)
logger.add_custom_level("NOTICE".to_string(), 35, "96".to_string())?;

// Use custom level
logger.log_custom("NOTICE", "Custom level message".to_string())?;

// Remove custom level
logger.remove_custom_level("NOTICE");
}

Custom Level Priority Rules

• Priority must be between 0-255
• Higher priority = more severe
• Custom levels integrate with standard filtering
• Duplicate names are rejected

Custom Level Colors

ANSI color codes:

• "30-37" - Standard colors
• "90-97" - Bright colors
• "1" - Bold
• "4" - Underline

Example:

#![allow(unused)]
fn main() {
logger.add_custom_level("AUDIT".to_string(), 28, "93".to_string())?;  // Bright yellow
logger.add_custom_level("SECURITY".to_string(), 48, "91;1".to_string())?;  // Bright red bold
}

Level Comparison

Levels can be compared:

#![allow(unused)]
fn main() {
assert!(Level::Trace < Level::Debug);
assert!(Level::Debug < Level::Info);
assert!(Level::Error > Level::Warning);

if record.level >= Level::Error {
    // Handle high severity
}
}

Level Priority Access

#![allow(unused)]
fn main() {
let priority = Level::Info.priority();  // Returns 20
let level = Level::from_priority(40);   // Returns Some(Level::Error)
}

Per-Level Configuration

Configure display options per level:

#![allow(unused)]
fn main() {
let mut config = LoggerConfig::default();

// Disable console for DEBUG level
config.console_levels.insert(Level::Debug, false);

// Disable colors for ERROR level
config.color_levels.insert(Level::Error, false);

// Disable timestamp for TRACE level
config.time_levels.insert(Level::Trace, false);

logger.configure(config);
}

Level Colors

Default colors:

• TRACE: Cyan (36)
• DEBUG: Blue (34)
• INFO: White (37)
• SUCCESS: Green (32)
• WARNING: Yellow (33)
• ERROR: Red (31)
• FAIL: Magenta (35)
• CRITICAL: Bright Red (91)

Customize colors:

#![allow(unused)]
fn main() {
let mut config = LoggerConfig::default();
config.level_colors.insert(Level::Info, "92".to_string());  // Bright green
config.level_colors.insert(Level::Error, "91;1".to_string());  // Bright red bold
logger.configure(config);
}

Best Practices

1. TRACE: Use for very detailed debugging, disabled in production
2. DEBUG: Development debugging, disabled in production
3. INFO: General information, enabled in production
4. SUCCESS: Highlight successful operations
5. WARNING: Potential issues that don't stop execution
6. ERROR: Errors that need attention but don't crash
7. FAIL: Operation failures that may need retry
8. CRITICAL: Severe errors that may crash the application

Examples

Development Logging

#![allow(unused)]
fn main() {
config.level = Level::Trace;  // Show everything
}

Production Logging

#![allow(unused)]
fn main() {
config.level = Level::Info;  // Hide TRACE and DEBUG
}

Error-Only Logging

#![allow(unused)]
fn main() {
config.level = Level::Error;  // Only errors and critical
}

Custom Audit Level

#![allow(unused)]
fn main() {
logger.add_custom_level("AUDIT".to_string(), 28, "93".to_string())?;
logger.log_custom("AUDIT", "User login successful".to_string())?;
}